The invention relates to a circuit arrangement for cooling charge air in a motor vehicle equipped with a turbocharger, and to a method for operating a circuit arrangement of this type. According to the prior art, to increase the power of engines, turbochargers are used in order to increase the throughput of air in the engine. In the compression needed for this, the air, designated below as charge air, is heated because of the compression in the turbocharger. To compensate for the loss of density associated with the heating of the charge air, i.e. in order to increase the air density, air coolers are used which are arranged at the front of the cooling module and serve for cooling the charge air. The charge air in this case flows through a heat exchanger, through which ambient air flows and which is consequently cooled. It is thereby possible to cool the charge air to a temperature which is approximately 15 K above the temperature of the ambient air.
It is furthermore known that the cooling of the charge air takes place via a coolant circuit, for example a low-temperature circuit, in which the coolant is cooled to very low temperatures. By means of this cold coolant, the charge air is cooled down to a predetermined cooling temperature in a charge air/coolant cooler. For the connection of the low-temperature circuit, there are two variants, namely an integration of the low-temperature circuit into a secondary circuit of the engine cooling system or a design in the form of a separate circuit.
If the engine output is to be further increased, the known supercharging systems have their limits, with respect to supercharging rates and response characteristics, at low load.
The object of the invention is to improve a circuit arrangement of the type mentioned in the introduction.